Drop malformed usernames
Keep strings that are 3–15 characters and contain only letters, digits, or underscores.
What you’ll practice
This Level 2 exercise focuses on filter predicate in the Built-ins curriculum. Solve the challenge prompt above using clear, idiomatic Python and the relevant language or standard-library tools.
Relevant Python reference: re — Regular expression operations, filter().
Sample Test Cases
valid_usernames(['ay','aya_7','bad name'])['aya_7']Further Reading
Reference Solution
Reveal Reference Solution
def valid_usernames(names: list[str]) -> list[str]: return list(filter(lambda n: 3 <= len(n) <= 15 and n.replace('_', '').isalnum(), names))Pro Tips & Keyboard Shortcuts
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